The pancreas is a compound gland with both exocrine and endocrine functions. Its long axis crosses the posterior abdominal wall at the level between the L1 and L2 vertebrae. The pancreas is composed of four parts:

All parts of the pancreas lie in the retroperitoneal space, except the distal end of the tail of the pancreas, which reaches the hilum of the spleen within the lienorenal ligament.

The head of the pancreas is the flattened enlarged portion that rests within the C-curve of the duodenum. The most inferior portion of the head is the uncinate process, which "hooks" to the left and lies posterior to the superior mesenteric artery and vein.